Impact of non-thermal processing on the nutritional quality and bioactive properties of industrial hempseed flours and protein isolate

Abstract

There is an unmet demand for plant-based ingredients with desirable nutritional, techno-functional properties, and health benefits. In this study, the composition, nutritional quality, and bioactives in industrial hempseed flours and protein isolate generated by milling, germination, isoelectric precipitation (IEP), and enzyme-assisted extraction (EAE) were evaluated. Moisture, ash, fat, protein, phytic acid, tannin, and trypsin inhibitor content of the hempseed flours and protein isolate were 2.80%–6.46%, 5.07%–28.89%, 0.00%–31.44%, 22.71%–89.94%, 0.55%–1.05%, 274.24–1300.76 μg/g, and 0.00–42.66 U/g, respectively. IEP resulted in the highest protein content (89.94%), indicative of its effective to isolate hempseed protein. Germination and IEP significantly reduced phytic acid and tannin contents by 1.53- and 3.63-fold, respectively. All processing methods improved in vitro protein digestibility (IVPD). SDS-PAGE analysis revealed comparable band patterns in milled and protein isolate, with a strong 50 kDa band attributed as edestin. Amino acid analysis showed that EAE augmented total essential amino acids, particularly protease. Milling and pronase treatment yielded the highest and lowest IVPD-corrected amino acid score (IVPDCAAS) of 76% and 47%, respectively. Milled and germinated flours contained varying amounts of γ-tocopherol, lutein, zeaxanthin, α-carotene, and β-carotene. Germinated flour exhibited elevated levels of total phenolic (14.36 mg/g), and flavonoid (1.76 mg/g) contents, FRAP, TEAC, and DPPH compared to the other flours suggesting superior antioxidant capacity. Strong positive correlations (r >0.70) were found between IVPD and phytic acid for the protein isolate, total phenolic content, and FRAP for IEP and germinated flours. Overall, hempseed flours with diverse properties could be produced using non-thermal processing.